In: Andrea Corradini; Bartek Klin (Hrsg.). Algebra and Coalgebra in Computer Science. Conference on Algebra and Coalgebra in Computer Science (CALCO-11), 4th, August 30 - September 2, Winchster, United Kingdom, Pages 145-160, Lecture Notes in Computer Science (LNCS), Vol. 6859, Springer Verlag, Berlin, 2011.